1. Field of the Invention
The present invention relates to a method and device that accelerates the placement of cutting guides in orthopaedic surgery, such as for instance total knee arthroplasty, uni knee arthroplasty or knee revision procedures, by taking the advantage of pre-operative patient images and intra-operative navigation systems and avoiding the drawbacks of patient specific guides manufactured as solid blocks, which do not offer enough flexibility, and avoiding drawbacks of navigation systems, which usually require additional steps in the surgical workflow.
2. Description of Related Art
It is known that patient specific guides are generated from preoperative CT (Computed Tomography) or MR (Magnetic Resonance) images, such that after surgical planning based on patient images, rapid machining of a specific guide is performed. The resulting guide is a solid block which is positioned in a supposedly unique and reproducible manner on the patient bone or cartilage surface, using surface contact areas, such that the guide contains holes or cutting slots adjusted precisely to their planned position on patient images. For instance, Radermacher K, and Staudte H. W. disclose in “Computer Assisted Orthopedic Surgery by means of Individual Templates”, Rau G. 1994, Medical Robotics and Computer Assisted Surgery, pp 42-48, a specific guide machined from CT images. Such patient specific guides require specific machining and a complex process where many errors can occur, which adds time and cost to the procedure. This is a major drawback. Such templates are usually disposable and machined for each patient which generates time and logistics issues before surgery. In addition, a difference between the bone or cartilage surface that is accessed intra-operatively and the surface of the bone or cartilage which is modeled from patient images may differ by one or several millimeters at some points. This can occur for instance because of the presence of osteophytes that are not easily visible on images, or because of the presence of small debris of soft tissues. They can create deviations of the orientation of the guides by several degrees from their planned position. In addition, the surgeon might have to change the planned position of an implant during the surgery to take into account the specificity of elements not visible or measurable on patient images, such as for instance the ligament behavior between the femur and the tibia in knee arthroplasty. And finally the patient specific guides for knee prosthesis require taking images, in addition to the knee joint, of the hip and ankle areas which are not standard radiology protocols for knee examination.
It is known to design adjustable templates from CT images for spine surgery with a small and minimal number of adjustments so that those adjustments can be performed by adjusting positions manually.
It is known that some navigation systems are tracking instrument positions during their adjustment, with respect to patient specific points, surfaces or articulations, and that some cutting blocks are tracked in real-time by navigation of bone cuts in particular for knee replacement procedures. It is known that some cutting blocks have mechanisms such that the cutting plane position can be adjusted with a few screws to reach precisely a target position defined on the basis of anatomical landmarks. Existing navigation systems require additional fixations to attach a tracker on the tibia and a tracker on the femur. This is a major drawback of navigation systems. Surgeons and patients are more and more reluctant to make additional holes into the bone for navigation purpose, because it creates additional scars, it increases the fragility of the bone and it adds time to the procedure. In addition, image free navigation systems do not offer the possibility to make a predetermination of the size of the implant preoperatively. In addition, some surgeons have difficulties to adjust the cutting blocks to predefined values, which require additional time and efforts.
The goal of the invention is to propose a device and method that solve the drawbacks of both patient-specific guides and navigation systems in order to offer a safe, easy-to-use and fast solution for positioning cutting guides on the basis of preoperative CT or MR images whilst maintaining enough flexibility to incorporate adjustments intra-operatively.